Drive mechanisms



Oct. 22, 1963 M. J. HUBER 3,107,493

DRIVE MECHANISMS Filed Feb. 5, 1962 2 Sheets-Sheet 2 22 \w I v INV OR fluid pressure employed.

3,107,493 Patented Oct. 22, 1963 ice 3,107,493 DRIVE MECHANISMS Mortimer J. Huber, 2141 N. Avon, St. Paul, Minn. Filed Feb. 5, 1962, Ser. No. 171,095 9 Claims. (Cl. 6097) This invention relates to an improvement in drive mechanisms and deals particularly :with a hydraulic motor structure capable of producing high starting torque.

During recent years many types of hydraulic motors have been produced which are capable of transforming hydraulic pressure into rotary movement. One such hydraulic motor includes a rotor housing including a rotor chamber having rounded lobes projecting inwardly from the peripheral wall of the chamber. An externally lobed rotor is rotatable within the housing, the rotor having one less lobe than does the peripheral housing and being so designed that the external lobes of the rotor continuously seal against the wall of the rotor chamber. The rotor is provided with one less lobe than the rotor chamber, and as a result as each lobe of the rotor enters the subsequent space between the lobes on the housing, the

axis of the rotor travels along an orbital path.

Fluid under pressure is supplied through a suitable valve arrangement attached to the rotor housing which acts against one-half of the lobes of the rotor to cause rotation of the rotor about its orbital path. The fluid forwardly of the lobes is then forced from the rotor chamber by the meshing of the lobes of the rotor with the lobes of the housing, this fluid being returned to a suitable reservoir and pump. Such orbital motors have been successfully commercially made and sold for a considerable number of years.

The starting torque of a motor of this type is dependent upon many things such as the size of the rotor and the For example, the starting torque of a rotor of given diameter could be increased by increasing its length. However, this is disadvantageous, as the longer the rotor is made, the more fluid must be forced into and out of the valve. This is particularly disadvantageous when less starting torque is'required, and the efliciency of the device is decreased when less starting torque is needed. I have found that by securing two or more similar motors in tandem, and by providing a suitable check valve system between the rotors, the starting torque of the device may be greatly increased without encountering the disadvantages which would be encountered in increasing the length of a single rotor.

I have found that by providing a series of check valves between the main rotor and an auxiliary rotor, the high pressure fluid will be first directed into the main rotor chamber, and if the resistance to rotation of the drive shaft exceeds a predetermined amount, the necessary check valves will be opened to direct fluid under pressure to the auxiliary rotor chamber as well. When this takes place, the area of the rotor lobes subjected to the high pressure will be correspondingly increased, resulting in a greatly increased starting torque. If the rotors are of the same size, and mounted for rotation in unison, the hydraulic force acting upon the lobes maybe substantially doubled to produce the increased force necessary to rotate the driven shaft.

In accomplishing the desired result, the check valve system must also provide that the fluid in'the auxiliary rotor be discharged or returned to the reservoir and means are provided to permit the fluid to be discharged during the compression stroke of the rotor lobes with a minimum of back pressure. It is a feature of the present invention that, if desired, several similar rotor units may be secured in tandem for rotation in unison as long ber to the earlier one.

as a check valve system is provided between each successive pair of rotor chambers so as to greatly increase the area of the lobes against which the fluid pressure is acting. In preferred form, the force necessary to open the check valve between each succeeding rotor is increased. With such an arrangement, when the start-ing torque is low, the fluid under pressure is applied to the first rotor only, the remaining rotor chambers running empty or with only suflicient fluid to provide lubrication. If the starting torque is somewhat higher, the check valves between the main rotor chamber and the first auxiliary chamber will open so that the fluid under pressure will also act upon the first auxiliary rotor to proportionally increase the starting torque. If the fluid pressure in the main rotor chamber and first auxiliary chamber are insufficient to create the necessary torque, the valves leading to the second auxiliary rotor chamber will open so that the fluid under pressure may act not only upon the main rotor but upon the first two auxiliary rotors. Thus any desired number of rotor :units within practical limits may be used to produce the necessary driving force.

It is also a feature of the present invention to provide a novel check valve arrangement which, in preferred form, includes a check valve housing including a series of passages capable of forming communication between the pockets between the internal lobes of the housing of one rotor housing and the space between the corresponding internal lobes of the next adjoining rotor. housing. A compound check valve is provided in each of these passages, the valve being so arranged that considerable hydraulic pressure is necessary to open the valve to permit the flow of fluid from one rotor housing to a successive rotor housing while relatively light pressure is required to open the compound check valve to permit the return flow of fluid from the successive rotor cham- As a result, the results which have been described above may be achieved.

These and other objects of the present invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of the specification;

FIGURE 1 is a side elevational view of the motor assembly showing the'general arrangement of parts therein.

FIGURE 2 is a sectional view'through the apparatus showing one of the rotor vent plates, the position of the section being indicated by the line 22 of FIGURE 1.

FIGURE 3 is a sectional view through one of the drive rotors, the position of the. section being indicated by the line 3--3 of FIGURE 1.

FIGURE 4 is a sectional view through the apparatus showing an end of the check valve housing, the position of the section being indicated by the line 4-4 of FIGURE 1.

FIGURE 5 is a sectional view through a portion of the check valve housing and vent plate, the position of the section being indicated by the line 5-5 of FlGURE 2.

FIGURE 6 is a view similar to FIGURE 5 showing the compound check valve in a position different from that illustrated in FIGURE 5.

FIGURE 7 is also a view similar to FIGURE 5 showing the compound check valve in still another position.

FIGURE 8 is a diagrammatic elevational view of a modified form of construction in which there are two auxiliary rotor units in place of one.

The torque converting device is indicated in general by the letter A and is shown in its assembly form in FIG- URE l of the drawings. The device includes a main 'valve body 10 of cylindrical form to which is connected a vent plate 11 which is provided with apertures leading from the interior of the valve body to the rotor housing 12. A second vent plate 11 is provided at the lower end of the rotor housing 12 and forms a communication between the rotor housing 12 and the check valve housing 13. An auxiliary rotor housing 14 which is similar to the rotor housing 12 is secured to the check valve housing 13. In the event only two rotor housings are to be secured in tandem, the end plate 15 is secured to the end of the rotor housing 14. If one or more additional rotor housings are to be secured in tandem, the additional structure added will include a vent plate 11, and additional check valve housing 13, and an additional rotor housing 14.

As is indicated in FIGURE 1 and in the sectional views 2, 3, and 4, it will be noted that the various elements are connected in proper series by cap screws 16 which extend through the margins of the various parts described in a direction parallel to the axes of these elements. In adding additional units, the length of these cap screws 16 is correspondingly increased.

For the purpose of explanation, it should be mentioned that orbital motors including the valve body 10, the vent plate 11, the rotor housing 12, and the end plate 15 are already in production. The present invention lies in the provision of additional rotor housings such as 14 through the addition of a corresponding vent plate 11 and check valve housing 13 for each added rotor housing.

As is best indicated in FIGURE 3 of the drawings, each rotor housing 14 is provided on its inner surface with a series of angularly spaced internally extending lobes 17, the housing illustrated being provided with seven such equally spaced lobes. A rotor 19 is supported within the rotor housing 14, the rotor 19 being provided with a series of external lobes 20 which are designed to extend between the lobes 17 of the housing and to fit snugly against the wall of the housing 14 between these lobes. The rotor 19 is provided with a number of lobes 20 which is one less than the number of internal lobes 17. The wall 21 of the rotor between the lobes 20 is substantially equal in radius to the outer surface 22 of the internal lobes 17, and the maximum diameter of the rotor 19 is substantially equal to the diametrical distance between the wall 23 of the housing 14 midway between a pair of lobes 17 and the outer surface 22 of the opposite lobe 17. As a result, the surfaces of the external rotor lobes 20 are at all times in sealing relation with the surfaces of the internal lobes 17 during rotation of the rotor.

The rotor 19 is supported upon a shaft 24, the axis of which is offset from the axis of the rotor housing 14. As a result, the shaft 24 travels in an eccentric or orbital path as it rotates. The means of driving is by hydraulic pressure between the housing 14 and the rotor in a manner later described.

As is also indicated in FIGURE 3, the housing 14 is provided with a series of bolt apertures 25 extending therethrough designed to accommodate the bolts 16. The apertures 25 are preferably equal in number to the number of internal lobes 17 and are centered with respect thereto.

As indicated in FIGURE 2 of the drawings, the vent plates 11 comprise flat disks having a central axial aperture 26 designed to accommodate the shaft 24. The disk 11 is provided with a series of angularly spaced apertures 27 extending therethrough designed to accommodate the bolts 16. Each vent plate 11 is also provided with a series of angularly spaced apertures 29 which communicate with the pockets formed between each pair of internal lobes 17 on the rotor housing 14 when the plate is attached to the rotor housing. Thus the valve body communicates through the apertures 29 with the space provided between each pair of adjoining lobes 17 in the uppermost rotor housing 12. The vent plate 11 which underlies the main rotor housing 12 also communicates with these same pockets.

As is indicated in FIGURE 4 of the drawings, the check valve housing 13 also includes a series of angularly spaced bolt apertures 30 which are designed to accommodate the bolts or cap screws 16. The housing 13 also includes the central aperture 31 through which the shaft 24 extends. The housing 13 also includes a series of angularly spaced valve cylinders 32 which are aligned with the apertures 29 of the vent plate 11 but which are of somewhat larger diameter than the apertures 29. The end of each cylinder 32 which is remote from the end abutting the vent plate 11 is provided with a portion 33 of reduced diameter which forms an abutment at the one end of each cylinder. As the axially aligned apertures 29 in the vent plate 11 are also of smaller diameter than the cylinders 32, an abutment is also formed at this end of each cylinder.

As is evident from the drawings, the axes of the bolts 16 are at substantially equal radius from the axes of the various elements 11, 12, 13, and 14. The cylinders 32 and the aligned apertures in the vent plates 11 are also at equal radius from the center of the members 12 and 14 in which they are formed.

The check valve housing 13 is provided with a series of parallel angularly spaced grooves 35 communicating with the interior of each cylinder 32 and extending from an end of the cylinder to the abutment 33 thereof. A valve sleeve 36 is slidably supported in each cylinder 32, movement of the valve sleeve in one direction being limited by the shoulder 37 formed between the upper end of the cylinder and the smaller diameter openings 29 in the vent plate. A spring 39 urges the valve sleeve 36 against the shoulder 37 in the assembled form of the unit. The valve sleeve 36 is provided with a smaller diameter portion 40 intermediate its ends. A tapered valve seat 41 is provided between one end of the reduced diameter portion 40 and the larger diameter portion 42 extending to the vent plate 11. A valve 43 having a head portion 44 freely slidable within the enlarged diameter portion 42 is provided with a tapered valve surface 45 which seats against the valve seat 41. The valve 43 also includes a valve stem 46 extending through the small diameter portion 40. If desired, angularly spaced guide ribs 47 may be provided either on the valve stem 46 or upon the reduced diameter portion 40 of the sleeve 36 to guide the valve 43 for axial movement.

A conical spring 49 is interposed between a snap ring 50 or other suitable shoulder on the vave stem 46 and the shoulder 51 formed between the reduced diameter portion 40 of the sleeve to urge the valve 43 against its seat. As is evidenced by the drawings, in speaking of the reduced diameter portion 40, reference is made to the internal diameter rather than the external diameter of the sleeve.

The spring 39 may be of any desired tension, but the spring preferably is of sufficient strength to hold the valve 1 sleeve 36 in closed position when the main rotor 12 is operating under normal conditions, and when the usual torque is being delivered to the driven shaft. For example, the spring 39 may be arranged to permit the valve 36 to open at fifty percent to seventy-five percent of the output of the maximum pump pressure driving the motor. On the other hand, the spring 49 is usually materially weaker, and will permit the opening of the valve 43 under relatively low pressure.

The operation of the device is as follows: Fluid under pressure from a suitable pressure supply is directed by the main valve 10 into the pockets formed between the rotor and the housing at various points where the space between the rotor and its housing may increase upon movement of the rotor along its orbital path. For example, if the rotor 19 is traveling in a clockwise direction, the size of the pockets 55, 56, and 57 is gradually increasing, and fluid may be introduced by the valve 10 through the corresponding ports 29 in the vent plate 11 to the pockets. The fluid under pressure is exerted against the rotor lobes 20 in a manner to rotate the rotor in a clockwise direction while the orbit of the rotor moves about its axis in a counter-clockwise direction. At the same time, the size of the pockets 59, 60, and 61 is decreasing to a corresponding extent, and the fluid from these pockets is being pumped by the rotor 19 through the corresponding ports 29 in the vent plate 11 and back into the main valve housing 10.

In the event the resistance to movement of the rotor 19 of the main rotor unit raises above a predetermined percentage of the maximum pressure delivered by the pump, this pressure is communicated through the vent plate 11 beneath the main rotor unit to the corresponding cylinders 32 in the check valve housing 13. As-a result, suflicient pressure is applied to the top of the valve sleeve 36 and the upper surface of the closed valve 43 to compress the springs 39 in the cylinders 32 located beneath the pockets 55, 56, and 57. This pressure moves the valve sleeve 36 downwardly toward the position indicated in FIGURE 7 of the drawings, providing communication between the ports 29 in the vent plate 11 and the grooves 35 in the walls of the pistons 32, permitting the fluid under pressure to bypass the valve sleeve 36 and to enter the corresponding pockets of the auxiliary rotor unit 14. The fluid under pressure then enters the corresponding pockets of both rotor units and provides an increased force against the walls of the rotor 19 in the pockets which are increasing in size. Fluid which is trapped in the pockets 59, 6t), and 61 of the auxiliary rotor housing =14 is forced by the rotor through the reduced diameter end 33 of the corresponding cylinders, raising the valves 43 as indicated in FIGURE 6 of the drawings, the fluid passing through the main rotor unit 12 and back into the main valve Iii.

In the previous discussion, no mention has been made of the seventh pocket 62. This is because in the position illustrated in FIGURE 2, the pocket 62 is substantially closed by the lobe 2%} of the rotor 19 which is in engagement with the base of the pocket.

After the proper starting torque has been applied to the rotor both in the rotor housings 12 and 14, the resistance to the rotation of the rotors within their respective rotor housings normally decreases. As this takes place, the pressure from the pressure supply within the main rotor 12 will decrease to a point where the spring 39' will urge the valve sleeve 36 toward the adjoining vent plate 11, thereby not opening so far upon rotation of the rotors and the amount of fluid which will bypass from the rotor unit 12 to the rotor unit 14 will decrease by expansion of the spring 35!, and the valve sleeve 36 finally will close. The fluid which has been trapped in the rotor chamber 14 will be forced by the rotation of the rotor 19 in this section past the valve 43 unt-il the amount of fluid in the rotor housing 12 will be only suificient to properly lubnicate the moving pants. At this point, the valves 36 are closed and the only additional power required to operate the main rotor and auxiliary rotor is in the friction between :the auxiliary rotor housing and the auxiliary rotor 1-; which is virtually negligible compared to the power developed.

In FIGURE 8 of the drawings, a modified form of construction is illustrated which differs only from the previously described construction in that an additional vent plate, an additional check valve housing, and an additional rotor housing and enclosed rotor is added. For the purpose of identification, the additional check valve housing has been identi led by the numeral 64 and the added rotor housing has been identified by the numeral 65. However, it should be understood that the elements 64 and 65 are similar to the units 13 and 14 except for a variation in the tension ofv the springs used in conjunction with the check valves.

t has been described that the check valves in the check valve housing 13 open only when the pressure exerted by the fluid supply pump exceeds a certain predetermined minimum. In a similar manner, the check valve housing 64 which would appear identical to the housing 133 is preferably provided with springs 39 which are some-what more resistant to compression than the springs in the section 13 so that the check valves in the housing 64 will only open if the pump pressure acting upon the rotors in the rotor units 12 and i4 exceeds a certain predetermined amount. If greater torque is required, the valves in the check valve chamber 64 will open and permit the high pressure fluid to enter the rotor unit 65 so that the fluid will exert an even greater pressure against the lobes of the respective rotors which are on one side of the rotor lobe which is sealed with respect to the wall portion 23 of the housing which is between two adjoining lobes 17.

In accordance with the patent statutes, I have described the principles of construction and operation of my improvement in drive mechanism, and while I have endeavored to set forth the best embodiment thereof, I desire to have it understood that changes may be made within the scope of the following claims without departing from the spirit of my invention.

I claim:

1. An attachment for use with an orbital motor comprising a main rotor housing including a series of equally angularly spaced inwardly extending lobes and an externally lobed rotor within said housing having one less lobe than said housing, said lobes of said housing being in substantial contact with the lobes of said rotor at all times as said rotor rotates relative to said housing, said orbital rotor including a fluid pressure supply, and a valve unit for directing fluid under pressure from said fluid pressure supply to areas between certain of said rotor and housing lobes to rotate said rotor relative to said housing and for relieving pressure in areas between others of said lobes of said housing and rotor to permit said relative rotation, said valve uni-t sequentially advancing the application of pressure to said areas upon relative rotation between said main rotor and main housing, said attachment including,

a second rotor housing similar to said main rotor housing,

"a second rotor in said second rotor housing similar to said first rotor and rotatable in unison therewith,

a check valve unit between said rotor housings,

passages through said check valve unit connecting the said areas of said main rotor-housing with the similar areas of the second rotor housing,

check valves in said passages operable upon an increase of pressure in certain areas within said main rotor housing to admit fluid under pressure to the similar areas within said second rotor housing,

means providing communication from the. areas between the lobes of said second rotor housing and said second rotor and said valve unit to permit the flow of fluid from said last named are-as, and

means closing said last named means when said last named areas are under pressure from said fluid pressure supply.

2. An attachment for use with an orbital motor comprising a main rotor housing including a series of equally angularly spaced inwardly extending lobes and an externally lobed rotor within said housing having one less lobe than said housing, said lobes of said housing being in substantial contact With the lobes of said rotor at all times as said rotor rotates relative to said housing, said orbital motor including a fluid pressure supply, and a valve unit for directing fluid under pressure from said fluid pressure supply to areas between certain of said rotor and housing lobes to rotate said rotor relative to said housing and for relieving pressure in areas between others of said lobes of said housing and rotor to permit said relative rotation, said valve unit sequentially advancing the application of pressure to said areas upon relative rotation between said main rotor and main housing, said attachment including,

a second rotor housing similar to said main rotor houss, a second rotor in said second rotor housing, similar to said first rotor and rotatable in unison there-with, a check valve unit between said rotor housing, passages through said check valve unit connecting the said areas of said main rotor housing with the similar areas of the second rotor housing, check valves in said passages operable upon an increase of pressure in certain said areas within said main rotor housing to admit fluid under pressure to the similar areas within said second rotor housing, second passage means providing communication from the areas between the lobes of said second rotor housing and said second rotor and the similar areas in said main rotor housing, and check valve means arranged to close communication through said second passage means except when pressure in certain of said areas in said second rotor housing exceeds the pressure in the corresponding areas of said main rotor housing. 3. The structure of claim 2 and in which said second passage means extends through said first check valves.

4. An attachment for use with an orbital motor comprising a main rotor housing including a main rotor chamber having a series of angularly spaced inwardly extending lobes, an externally lobed main rotor rotatable within said rotor chamber and having one less lobe than said housing, said lobes of said rotor being in substantial contact with the lobes of said housing as the rotor rotates relative to said housing, rotation of said main rotor about an orbital path creating pockets between said housing and said rotor which increase in size on one side of said rotor and decrease in size on the other side thereof, a fluid pressure supply, a valve unit for directing fluid under pressure from said pressure supply to the pockets increasing in size and for receiving return fluid from the pockets decreasing in size as the rotor rotates about its orbital path, the attachment including a second rotor housing similar to said main rotor housa second rotor similar to said main rotor and rotatable in said second rotor housing, a check valve housing secured between said main rotor housing and second rotor housing, means securing said main and second rotor housings in coaxial relation, connecting means extending through said check valve housing and connecting said main and second rotors for rotation in unison in coaxial alignment, said check valve housing having angularly spaced passages connecting the space between each pair of lobes of the main housing with the space between the corresponding lobes of the second rotor housing, first normally closed check valve in each said passage operable to open the corresponding passage when the pressure in the pockets of increasing size in said main rotor housing exceeds a predetermined maximum to permit the flow of fluid under pressure to the corresponding pockets of the second rotor housing, secondly normally closed check valve in each said passage held in closed position when the pressure in pockets of increasing size in the main rotor housing exceeds that in the corresponding pockets of the second rotor housing and operable when the pressure in the pockets of decreasing size in the second rotor housing exceeds that of the corresponding pockets in the main rotor housing to open to permit a return flow of fluid. 5. The structure of the claim 4 and in which said second check valves are carried by said first check valves.

6. The structure of claim 4 and in which said first check valve includes a sleeve slidable in each. said passage,

by pass passage means closed by said sleeve in said normally closed position of said first check valve and providing communication past said sleeve in open position thereof,

said second check valve being slidably supported by said sleeve and normally closing the passage through said sleeve.

7. The structure of claim 6 and including relatively strong resilient means resisting slidable movement of said sleeve, and relatively weak resilient means resisting slidable movement of said second valve in said sleeve.

8. An attachment for use with an orbital motor comprising a main rotor housing including a main rotor chamber having a series of angularly spaced inwardly extending lobes, an externally lobed main rotor rotatable within said rotor chamber and having one less lobe than said housing, said lobes of said rotor being in substantial contact with the lobes of said housing as the rotor rotates relative to said housing, rotation of said main rotor about an orbital path creating pockets between said housing and said rotor which increases in size on the other side thereof, a fluid pressure supply, a valve unit for directing fluid under pressure from said pressure supply to the pockets increasing in size and for receiving return fluid from the pockets decreasing in size as the rotor rotates about its orbital path, the attachment including a second rotor housing similar to said main rotor housa second rotor similar to said main rotor and rotatable in said second rotor housing,

a check valve housing secured between said main rotor housing and second rotor housing,

means securing said main and second rotor housings in coaxial relation, connecting means extending through said check valve housing and connecting said main and second rotors for rotation in unison in coaxial alignment,

said check valve housing having angularly spaced passages connecting the space between each pair of lobes of the main housing with the space between the corresponding lobes of the second rotor housing,

compound check valves in said passages, said check valves normally closing said passages from the flow of fluid in either direction, said compound check valves including, means resisting the flow of fluid from said pockets of increasing size in said main rotor housing to the corresponding pockets of said second rotor housing until the fluid pressure in said main rotor housing exceeds a predetermined maximum at which time the resisting means permits fluid flow into said second rotor housing, and

means resisting the flow of fluid from the pockets in said second rotor housing to the corresponding pockets of the main rotor housing until the fluid pressure in a pocket in the second rotor housing exceeds the pressure in the corresponding pocket of the main rotor housing, whereupon return flow through said passages may take place.

9. The structure of claim 8 and including a third rotor housing similar to the second rotor housing and a second check valve housing similar to the first-and connecting the second and third rotor housings and controlling the flow of fluid therebetween.

References Cited in the file of this patent UNITED STATES PATENTS 1,994,974 Wiedrnann Mar. 19, 1935 2,370,526 Doran Feb. 27, 1945 2,374,588 Doran Apr. 24, 1945 

1. AN ATTACHMENT FOR USE WITH AN ORBITAL MOTOR COMPRISING A MAIN ROTOR HOUSING INCLUDING A SERIES OF EQUALLY ANGULARLY SPACED INWARDLY EXTENDING LOBES AND AN EXTERNALLY LOBED ROTOR WITHIN SAID HOUSING HAVING ONE LESS LOBE THAN SAID HOUSING, SAID LOBES OF SAID HOUSING BEING IN SUBSTANTIAL CONTACT WITH THE LOBES OF SAID ROTOR AT ALL TIMES AS SAID ROTOR ROTATES RELATIVE TO SAID HOUSING, SAID ORBITAL ROTOR INCLUDING A FLUID PRESSURE SUPPLY, AND A VALVE UNIT FOR DIRECTING FLUID UNDER PRESSURE FROM SAID FLUID PRESSURE SUPPLY TO AREAS BETWEEN CERTAIN OF SAID ROTOR AND HOUSING LOBES TO ROTATE SAID ROTOR RELATIVE TO SAID HOUSING AND FOR RELIEVING PRESSURE IN AREAS BETWEEN OTHERS OF SAID LOBES OF SAID HOUSING AND ROTOR TO PERMIT SAID RELATIVE ROTATION, SAID VALVE UNIT SEQUENTIALLY ADVANCING THE APPLICATION OF PRESSURE TO SAID ARAS UPON RELATIVE ROTATION BETWEEN SAID MAIN ROTOR AND MAIN HOUSING, SAID ATTACHMENT INCLUDING, A SECOND ROTOR HOUSING SIMILAR TO SAID MAIN ROTOR HOUSING, A SECOND ROTOR IN SAID SECOND ROTOR HOUSING SIMILAR TO SAID FIRST ROTOR AND ROTATABLE IN UNISON THEREWITH, A CHECK VALVE UNIT BETWEEN SAID ROTOR HOUSING, PASSAGES THROUGH SAID CHECK VALVE UNIT CONNECTING THE SAID AREAS OF SAID MAIN ROTOR HOUSING WITH THE SIMILAR AREAS OF THE SECOND ROTOR HOUSING, CHECK VALVES IN SAID PASSAGES OPERABLE UPON AN INCREASE OF PRESSURE IN CERTAIN AREAS WITHIN SAID MAIN ROTOR HOUSING TO ADMINT FLUID UNDER PRESSURE TO THE SIMILAR AREAS WITHIN SAID SECOND ROTOR HOUSING, MEANS PROVIDING COMMUNICATION FROM THE AREAS BETWEEN THE LOBES OF SAID SECOND ROTOR HOUSING AND SAID SECOND ROTOR AND SAID VALVE UNIT TO PERMIT THE FLOW OF FLUID FROM SAID LAST NAMED AREAS, AND MEANS CLOSING SAID LAST NAMED MEANS WHEN SAID LAST NAMED AREAS ARE UNDER PRESSURE FROM SAID FLUID PRESSURE SUPPLY. 